1. Field of the Invention
The present invention relates to a zoom lens barrel.
2. Description of the Related Art
In general, a zoom lens barrel of a zoom compact camera, etc., includes a rotary cylinder (rotary feed cylinder) which is rotatable relative to a camera body, and a linear movement cylinder which is provided in the rotary cylinder so as not to rotate, wherein the rotary cylinder and the linear movement cylinder are relatively rotatable and are movable together in the optical axis direction. Generally speaking, the rotary cylinder and the linear movement cylinder are provided, on their rear ends in the optical axis direction, with a pawl or flange and a circumferential groove, so that the rotary cylinder and the linear movement cylinder are guided so as to relatively rotate through the engagement of the pawl or flange and the circumferential groove. Consequently, a sufficient strength of the cylinders at the rear ends thereof can be easily obtained, but it is difficult to obtain a sufficient strength at the front ends thereof. For instance, if the linear movement cylinder is provided with a through-groove which is adapted to rotate another rotary feed cylinder provided within the linear movement cylinder, the strength of the linear movement cylinder is reduced due to the presence of the through-groove. Consequently, the linear movement cylinder tends to be deflected or inclined toward the optical axis, particularly at the front end thereof. The deflection or inclination of the linear movement cylinder causes an error in the photographing optical system. To solve these problems, in conventional zoom lens barrels, the thickness of the barrel is increased, the length of the portion of the linear movement cylinder on which no through-groove is formed is increased, or reinforcing rings are provided at the front ends of the rotary cylinder and the linear movement cylinder. However, these solutions result in an increase in the size or in the number of the elements of the lens barrel.
It is an object of the present invention to provide a small and simple zoom lens barrel having an increased strength.
In order to achieve the above-mentioned object, a zoom lens barrel is provided, including a rotary feed cylinder which is moved in an optical axis direction while being rotated; a linear movement cylinder which is provided within the rotary feed cylinder and which is guided to linearly move in the optical axis direction; and a connecting structure for connecting the linear movement cylinder to the rotary feed cylinder so as to relatively rotate and so as not to relatively move in the optical axis direction. The connecting structure includes at least two circumferential grooves centered about the optical axis, which are provided on one of the inner peripheral surface of the rotary feed cylinder or the outer peripheral surface of the linear movement cylinder, at different positions in the optical axis direction; and at least two radially extending engagement pawls which are provided on the other of the inner peripheral surface of the rotary feed cylinder or the outer peripheral surface of the linear movement cylinder, at different positions in the optical axis direction and which correspond to the at least two circumferential grooves, the engagement pawls being engaged in the circumferential grooves so as to slide in the circumferential direction and so as not to relatively move in the optical axis direction.
With this arrangement, since the connecting portion between the rotary feed cylinder and the linear movement cylinder is made of a plurality of circumferential grooves and engagement pawls, formed at different axial positions, the degree of connection is enhanced. Thus, a sufficient strength of the lens barrel over the entire axial length can be provided without increasing the thickness or the axial length of the barrel or providing reinforcing rings.
To provide sufficient strength, it is preferable that the at least two circumferential grooves are located on opposite sides of either the inner peripheral surface of the rotary feed cylinder or the outer peripheral surface of the linear movement cylinder, in the optical axis direction, in which the circumferential grooves are formed.
In an embodiment, the at least two engagement pawls are provided on the linear movement cylinder, the linear movement cylinder being provided with a through-groove inclined with respect to the optical axis, the at least two engagement pawls being located on opposite sides of the through-groove in the optical axis direction.
Preferably, the connecting structure includes a plurality of coaxial engagement pawls at different circumferential positions, corresponding to the at least two circumferential grooves.
To facilitate assembly and disassembly, it is preferable that the at least two circumferential grooves are formed on the inner peripheral surface of the rotary feed cylinder, the at least two engagement pawls being formed on the outer peripheral surface of the linear movement cylinder, the rotary feed cylinder being provided on the inner peripheral surface thereof with a pawl engagement/disengagement groove which extends from the rear end thereof to the frontmost circumferential groove, of the at least two circumferential grooves, in parallel with the optical axis, so that the engagement pawls can be disengageably engaged with the at least two circumferential grooves in the optical axis direction at a specific relative angular position between the rotary feed cylinder and the linear movement cylinder.
In an embodiment, the inner peripheral surface of the rotary feed cylinder, on which the circumferential grooves are formed, is provided with an axial groove different from the pawl engagement/disengagement groove, the axial groove extending in parallel with the optical axis and intersecting the circumferential grooves, wherein the length of the engagement pawls in the circumferential direction are larger than the width of the axial groove. Consequently, no disengagement of the engagement pawls occurs at a portion other than the pawl engagement/disengagement groove.
According to another aspect of the present invention, a zoom lens barrel is provided, having a pair of cylindrical members of different diameters which are connected so as to relatively rotate and so as not to relatively move in an optical axis direction, wherein a connecting structure for connecting the pair of cylindrical members includes at least two circumferential grooves centered about the optical axis, which are provided on one of an inner peripheral surface of a larger diameter cylindrical member of the pair of cylindrical members, and an outer peripheral surface of a smaller diameter cylindrical member of the pair of cylindrical members, at different positions in the optical axis direction; and at least two radially extending engagement pawls which are provided on the other of the inner peripheral surface of the larger diameter cylindrical member and the outer peripheral surface of the smaller diameter cylindrical member, at different positions in the optical axis direction, and which correspond to the at least two circumferential grooves, the engagement pawls being engaged in the circumferential grooves so as to slide in the circumferential direction and so as not to relatively move in the optical axis direction.
According to another aspect of the present invention, a connecting structure of a pair of cylindrical members used for a zoom lens barrel is provided, the pair of cylindrical members having different diameters, the connecting structure including at least two circumferential grooves centered about the optical axis, which are provided on one of an inner peripheral surface of a larger diameter cylindrical member of the pair of cylindrical members, and an outer peripheral surface of a smaller diameter cylindrical member of the pair of cylindrical members, at different positions in the optical axis direction; and at least two radially extending engagement pawls which are provided on the other of the inner peripheral surface of the larger diameter cylindrical member and the outer peripheral surface of the smaller diameter cylindrical member, at different positions in the optical axis direction and which correspond to the at least two circumferential grooves, the engagement pawls being engaged in the circumferential grooves so as to slide in the circumferential direction and so as not to relatively move in the optical axis direction.
To provide sufficient strength, it is preferable that the at least two circumferential grooves are located on opposite sides of one of the larger diameter cylindrical member and the smaller diameter cylindrical member, in the optical axis direction, in which the circumferential grooves are formed.
In an embodiment, the at least two engagement pawls are provided on the smaller diameter cylindrical member, the smaller diameter cylindrical member being provided with a through-groove inclined with respect to the optical axis, the at least two engagement pawls being located on opposite sides of the through-groove in the optical axis direction.
Preferably, the connecting structure includes a plurality of coaxial engagement pawls at different circumferential positions, corresponding to the at least two circumferential grooves.
To facilitate assembly, it is preferably that the at least two circumferential grooves are formed on the inner peripheral surface of the larger diameter cylindrical member, the at least two engagement pawls being formed on the outer peripheral surface of the smaller diameter cylindrical member, the larger diameter cylindrical member being provided on the inner peripheral surface thereof with a pawl engagement/disengagement groove which extends from the rear end thereof to the frontmost circumferential groove, of the at least two circumferential groove, in parallel with the optical axis, so that the engagement pawls can be disengageably engaged with the at least two circumferential grooves in the optical axis direction at a specific relative angular position between the larger diameter cylindrical member and the smaller diameter cylindrical member.
In an embodiment, the inner peripheral surface of the larger diameter cylindrical member on which the circumferential grooves are formed, is provided with an axial groove different from the pawl engagement/disengagement groove, the axial groove extending in parallel with the optical axis and intersecting the circumferential grooves, the length of the engagement pawls in the circumferential direction being larger than the width of the axial groove. The present disclosure relates to subject matter contained in Japanese Patent Application No.11-305222 (filed on Oct. 27, 1999) which is expressly incorporated herein by reference in its entirety.